touch

, settime

用法概要

描述

The touch utility sets the access and modification times of each file. The
file operand is created if it does not already exist.

The time used can be specified by -ttime, by -ddate_time, by
the corresponding time fields of the file referenced by -rref_file, or by the
time_spec operand. If none of these are specified, touch uses the current time.

If neither the -a nor -m options are specified, touch updates both the
modification and access times.

A user with write access to a file, but who is not
the owner of the file or a super-user, can change the modification and
access times of that file only to the current time. Attempts to set
a specific time with touch results in an error.

The settime utility is equivalent to touch-c [time_spec] file.

选项

The following options are supported in the touch and settime utilities:

touch

The following options are supported for the touch utility:

-a

Changes the access time of file. Does not change the modification time unless -m is also specified.

-c

Does not create a specified file if it does not exist. Does not write any diagnostic messages concerning this condition.

-ddate_time

Uses the specified date_time instead of the current time. The option-argument must be a string of the form:

YYYY-MM-DDThh:mm:SS[.frac][tz]

or

YYYY-MM-DDThh:mm:SS[,frac][tz]

where

YYYY is at least four decimal digits giving the year

MM, DD, hh, mm, and SS are as with -ttime

T is either the letter T or a single SPACE character

[.frac] and [,frac] are either empty, or a period (.) or a comma (,) respectively, followed by one or more decimal digits, specifying a fractional second

[tz] is either empty, signifying local time, or the letter Z, signifying UTC. If [tz] is empty, the resulting time is affected by the value of the TZ environment variable

-m

Changes the modification time of file. Does not change the access time unless -a is also specified.

-rref_file

Uses the corresponding times of the file named by ref_file instead of the current time.

-ttime

Uses the specified time instead of the current time. time is a decimal number of the form:

[[CC]YY]MMDDhhmm[.SS]

where each two digits represent the following:

MM

The month of the year [01-12].

DD

The day of the month [01-31].

hh

The hour of the day [00-23].

mm

The minute of the hour [00-59].

CC

The first two digits of the year.

YY

The second two digits of the year.

SS

The second of the minute [00-61].

Both CC and YY are optional. If neither is given, the current year is assumed. If YY is specified, but CC is not, CC is derived as follows:

If YY is:

CC becomes:

69-99

19

00-38

20

39-68

ERROR

The resulting time is affected by the value of the TZ environment variable. The range of valid times is the Epoch to January 18, 2038.

The range for SS is [00-61] rather than [00-59] because of leap seconds. If SS is 60 or 61, and the resulting time, as affected by the TZ environment variable, does not refer to a leap second, the resulting time is one or two seconds after a time where SS is 59. If SS is not given, it is assumed to be 0.

settime

The following option is supported for the settime utility:

-fref_file

Uses the corresponding times of the file named by ref_file instead of the current time.

操作数

The following operands are supported for the touch and settime utilities:

file

A path name of a file whose times are to be modified.

time_spec

Uses the specified time_spec instead of the current time. This operand is a decimal number of the form:

MMDDhhmm[YY]

where each two digits represent the following:

MM

The month of the year [01-12].

DD

The day of the month [01-31].

hh

The hour of the day [00-23].

mm

The minute of the hour [00-59].

YY

The second two digits of the year.

YY is optional. If it is omitted, the current year is assumed. If YY is specified, the year is derived as follows:

YY

Corresponding Year

69-99

1969-1999

00-38

2000-2038

39-68

ERROR

If no -d, -r, or -toption is specified, at least two operands are specified, and the first operand is an eight- or ten-digit decimal integer, the first operand is assumed to be a time_spec operand. Otherwise, the first operand is assumed to be a file operand.

用法

See largefile(5) for the description of the behavior of touch when encountering files greater
than or equal to 2 Gbyte ( 231 bytes).

环境变量

See environ(5) for descriptions of the following environment variables that affect the execution of
touch: LANG, LC_ALL, LANG, LC_ALL, LC_CTYPE, LC_MESSAGES, and NLSPATH.

TZ

Determine the timezone to be used for interpreting the time or date_time option-argument or the time_spec operand.

退出状态

The following exit values are returned:

0

The touch utility executed successfully and all requested changes were made.

>0

An error occurred. The touch utility returned the number of files for which the times could not be successfully modified.

另请参见

附注

Users familiar with the BSD environment find that for the touch utility, the
-f option is accepted but ignored. The -f option is unnecessary because touch
succeeds for all files owned by the user regardless of the permissions on
the files.